Four person are feared dead and a major incident has been declared following the collapse of a building at Didcot A Power Station in Oxfordshire
South Central Ambulance Service said it has sent its hazardous areas response team to the site, as well as three ambulances and the air ambulance.
A spokesman said: "We are describing it as a major incident."
Thames Valley Police confirmed officers were at the scene but have not released further details until the next of kin had been informed.
Chief fire officer Dave Etheridge described the collapse as a "very severe incident" which left one dead, five injured and three unaccounted for.
He expressed "absolute sympathy and deep thoughts to all the families involved".
He added: "We are doing our very best to secure the return of their loved ones as soon as we can."
Update 23 February 2016 at 21:29:43 from the scene
Statement from RWE Generation UK
We can confirm that shortly after 4pm this afternoon part of the Boiler House at our former Didcot A Power Station site in Oxfordshire collapsed while an external demolition contractor was working in it.
It is with great sadness that we understand that there has been one fatality, four people have been taken to hospital and 3 people are currently missing and unaccounted for.
Our thoughts are with the families of all those involved in this tragedy. We will provide updates as we receive them.
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We are working with the emergency services who are currently on site to understand the cause of this collapse.